©1999 Navia Aviation AS 21833-3.4 Maintenance Procedures
OPERATING MANUALNORMARC 7013
INSTRUMENT LANDING SYSTEM
C-13
6. Measure the time (in microseconds) between the center of the oscilloscope and the scope
trace.
7. Confirm that the time measured is within the operating tolerance of chapter 3.
8. Restore the equipment to normal operation.
5-20 SHUTDOWN AND FAR-FIELD MONITOR TIME DELAYS.
a. Object.
This procedure provides a method to determine the times of the shutdown and far-field moni-
tor (FFM) time delays.
b. Discussion.
The time that a facility is permitted to radiate outside monitor alarm limits must be short. This
is to protect aircraft in the final stages of approach from prolonged exposure to possible signal
error. The different time delays are defined below.
(1) Shutdown delay. This delay is the total time a facility is allowed to radiate with a continu-
ous monitor alarm. For dual equipment, this delay includes the transfers from main to standby
to shutdown.
(2) Far-field monitor delay. This time delay applies to localizers that have a far-field moni-
tor(s) and is the total time between the initiation of a continuous far-field monitor alarm and a
localizer shutdown or to CAT I downgrade. This time delay is relatively long, as the far-field
monitor experiences numerous momentary alarms due to multipath from taxiing and overflying
aircraft.
c. Test Equipment Required.
A device suitable for measuring elapsed time.
d. Conditions.
A facility shutdown is required for this check.
e. Detailed Procedure.
1. Shutdown delay
(a) Initiate a continuous monitor alarm and measure the time between initiation of the alarm
condition(s) and localizer shutdown.
(b) Compare this measurement with the standard and tolerance contained in paragraph 3-21,
and correct, if necessary. Record shutdown delay on the appropriate form.
(c) Return facility to service.
(3) Far-field monitor delay. Initiate a continuous alarm at the far-field monitor(s). This may
be accomplished by removing one of the navigation tones at the localizer, or by causing an
alarm at the far-field monitor itself.
(a) Measure the time between initiation of the alarm condition(s) and localizer shutdown.
(b) Measure the time between the localizer shutdown event and the visual alrarm.
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